Since a laminate glass is scarcely scattered in debris even if being broken by receiving outside impact and is thus safe, the laminate glass has been used widely for a window glass of vehicles such as automobiles; aircrafts; buildings and the like. Examples of such a laminate glass are those which are obtained by inserting an interlayer film for a laminate glass comprising polyvinyl acetal resin such as polyvinyl butyral resin plasticized by a plasticizer between at least one pair of glasses and uniting such a film with glasses.
Although the laminate glass using such an interlayer film for a laminate glass is excellent in safety, it has a disadvantageous point that it is inferior in heat-shielding property. Generally, infrared ray (IR) with wavelength at shortest 780 nm, which is longer than that of visible light, among the light rays, has energy dose as low as about 10% of that of ultraviolet (UV) ray but has a significant thermal effect and if once absorbed in a substance, IR is released in form of heat to result in temperature increase and therefore, it is called as thermal beam. Accordingly, among light rays coming in through a front glass or side glass of an automobile, if IR having significant thermal effect is shielded, the heat-shielding effect is increased and the temperature increase in the inside of the automobile can be suppressed.
As such a glass which shields IR having significant thermal effect, for example, a heat ray-cutting glass has been commercialized. The heat ray-cutting glass is developed aiming to shield direct sun lights and obtained by forming a multilayer coating of metal/metal oxide on the surface of a glass plate by metal evaporation, sputtering or the like. However, such a multilayer coating is susceptive of scratching from the outside and inferior in chemical resistance, so that a method of obtaining the laminate glass laminating an interlayer film of a plasticized polyvinyl butyral resin film or the like has been employed.
However, the heat ray-cutting glass has problems that the glass is expensive, deteriorated in the transparency (visible light transmittance) because of thick thickness of the multilayer coating, and highly colorized because of absorption in a visible light region. Further, there are other problems that the adhesion between the multilayer coating and the interlayer film is decreased to cause separation and whitening of the interlayer film and that the multilayer coating layer inhibits transmittance of electromagnetic wave and interferes with communication functions of a mobile phone, a car navigation system, a garage opener, an electronic toll collection system, and the like.
For example, Patent Document No. 1 and Patent Document No. 2 proposes a laminate glass obtained by inserting a polyester film on which a thin film of a metal and/or metal oxide is formed or evaporated between plasticized polyvinyl butyral resin sheets. However, these laminate glasses have a problem in the adhesion between the plasticized polyvinyl butyral resin sheets and the polyester film to result in not only separation in the interfaces but also insufficiency of electromagnetic wave transmittance.
Further, Patent Document No. 3 discloses a method of obtaining electromagnetic wave transmittance by dispersing a metal oxide having heat-shielding property in the interlayer film. However the laminate glass comprising such an interlayer film for a laminate glass obtained by the described method has a problem that the laminate glass is discolored to be yellow to decrease the visible light transmittance after a durability test to light in some cases and thus it is expected that the laminate glass is scarcely allowed for use as an automotive front glass whose visible light transmittance is regulated in the lower limit.    Patent Document No. 1: Japanese Kokoku Publication Sho-61-52093    Patent Document No. 2: Japanese Kokai Publication Sho-64-36442    Patent Document No. 3: Japanese Kokai Publication 2001-302289